Since the Gratzel group in Swiss reported a dye-sensitized solar cell in 1991, which can be prepared at low costs, to replace the commercialized amorphous silicon solar cell, there have been active researches on improving photo-conversion efficiency of the dye-sensitized solar cell.
With respect to principle for operation of the dye-sensitized solar cell, when photosensitive dye molecules adsorbed to an n-type nanoparticle oxide semiconductor are exposed to the sunlight, electrons are excited. The excited electrons are transferred to a conductive transparent substrate through the oxide semiconductor. The transferred electrons are transferred to a counter electrode through an external circuit so that currents flow. At this time, holes formed in the photosensitive dye molecules are reduced again by a redox electrolyte. During this process, the oxidized electrolyte component receives electrons from the counter electrode so as to be reduced. The maximum efficiency of the dye-sensitized solar cell operating based on the above-described principle is currently about 11%.
Researches for promoting commercialization of a dye-sensitized solar cell are being actively conducted over the whole world. Five (5) representative strategies for the commercialization of the dye-sensitized solar cell can be summarized as follows: (i) research on a photosensitive dye, which can absorb light of entire wavelength bands including a visible light region and an infrared region; (ii) research on controlling a structural form of an n-type nanoparticle oxide semiconductor in order to maximize adsorption of a photosensitive dye and injection of electrons; (iii) research on a redox electrolyte which induces stable and effective reduction; (iv) research for replacing an expensive platinum electrode; and (v) research on improvement of stability of a solar cell.
With respect to the strategy (ii) among the five (5) representative strategies above, Korean Patent Application Publication No. 10-2010-0126986, which relates to a “photoelectrode using a conductive non-metallic film and a dye-sensitized solar cell containing the same,” and others disclose more effective preparation of a photoelectrode for a dye-sensitized solar cell. However, there have no sufficient researches conducted on improving the photo-conversion efficiency of the dye-sensitized solar cell by preparing a hybrid material by using carbons and other materials, and then, using the hybrid material as a part of the photoelectrode for the dye-sensitized solar cell.